Journal of the Society of Motion Picture Engineers (1930-1949)

May, 1930] WESTERN ELECTRIC RECORDING SYSTEM 529 in the development of the positive sound track, in fact I believe there is more latitude in the development of the positive sound track than you would tolerate in the development of a picture. MR. FETTER: I think I said in the paper that the control of the gamma was not so critical as was popularly supposed. I believe the tolerance of 0.8 to 1.2 does introduce a 5 per cent harmonic. Of course, we always like to keep it as near unity as possible. Under practical laboratory conditions, it is difficult to realize the desired theoretical values but the closer we can keep to unity the safer we are. With regard to picture gammas and their variations I do not know enough to guess how far you can go in terms of gamma. DR. CLARK: I would like to ask Mr. Fetter what experience he has had with other types of emulsion than cine positive. MR. FETTER: You mean for positive or negative recording? DR. CLARK: For negative recording. MR. FETTER: I participated in some experiments in Hollywood in February and March of 1929, in which we made some comparisons between ordinary stock and another stock. That was while Eastman was doing development on the Reprotone stock, and probably the stock we were experimenting with had not reached the final desired stage. At that time I believe that while our measurements and experiments did not carry us to very accurate conclusions — and possibly when making the tests there were variables which we did not consider — there was not a great deal of difference between the two, but that, as I say, was before they had reached the final answer. I do not know what the best emulsions are. In the recording work here we have been sticking to something which we knew we had available and we did not want to hazard a project by introducing experimental emulsions. MR. WHITEHOUSE: Mr. Fetter has told us that the amplification system of the light valve responds up to 7000 cycles. One thing was not mentioned: What is the net result on the positive print; is there any film transfer loss? Assuming you can get so many cycles on your negative is there any loss in high frequencies in printing, and is there any loss in projection? Do you get 7000 cycles as a commercial result in the theater? MR. FETTER: We do know there is a film transfer loss. If we apply exposures through the light valve we know that we can record on the film equal amplitudes from the very lowest frequencies up to the neighborhood of 7000 cycles. The film is developed, printed, and projected. We do know that we experience loss only in the high end of the frequency spectrum. We do not maintain that we can put into a theater the exact equivalent of the 6000 to 7000 cycles range that we actually record. Loss may be due to limitations of the emulsion, to reflections and refractions in printing, and there may be other causes. Of course, you can take a single frequency film and actually hear 7000 cycles projected in a regular projecting machine, but that does not tell you anything about its true proportion. I should say that if you can produce in the theater a record which is absolutely flat up to 5000 cycles, in the light of the present art, it would be quite satisfactory. Of course that question is also tied up with the theater and with the position of the horns in the theater. High frequencies are very directional, low frequencies have a habit of spreading out. MR. EVELEIGH: Mr. Fetter spoke about re-recording from gramophone